Yes I came to post exactly this, and found your comment, so will reply instead. The bug doesn't seem to be obscure. It is there in the right place. Someone thinking about checking "why some players are attacked more often?" would probably choose this as the first place to double check, since it is directly related to selecting the player for attack.
Maybe the most occult part of this is figuring out that the unique IDs assigned to the players play a role.
> The bug doesn't seem to be obscure. It is there in the right place.
Well, there is a larger bug -- the entire algorithm, functioning properly, still won't behave the way this letter says that it should. It's not clear what it's designed to do, but it's very obvious that it doesn't do what the description says it does.
Maybe the most occult part of this is figuring out that the unique IDs assigned to the players play a role.